The Effect of Interlayer Anion Grafting on Water Oxidation Electrocatalysis: A Comparative Study of Ni‐ and Co‐Based Brucite‐Type Layered Hydroxides, Layered Double Hydroxides and Hydroxynitrate Salts

Abstract

The urge for carbon-neutral green energy conversion and storage technologies has invoked the resurgence of interest in applying brucite-type materials as low-cost oxygen evolution reaction (OER) electrocatalysts in basic media. Transition metal layered hydroxides belonging to the brucitetype structure family have been shown to display remarkable electrochemical activity. Recent studies on the earth-abundant Fe 3 + containing mössbauerite and Fe 3 + rich CoÀ Fe layered oxyhydroxide carbonates have suggested that grafted interlayer anions might play a key role in OER catalysis. To probe the effect of such interlayer anion grafting in brucitelike layered hydroxides, we report here a systematic study on the electrocatalytic performance of three distinct Ni and Co brucite-type layered structures, namely, (i) brucite-type M-(OH) 2 without any interlayer anions, (ii) LDHs with free interlayer anions, and (iii) hydroxynitrate salts with grafted interlayer anions. The electrochemical results indeed show that grafting has an evident impact on the electronic structure and the observed OER activity. Ni-and Cohydroxynitrate salts with grafted anions display notably earlier formations of the electrocatalytically active species. Particularly Co-hydroxynitrate salts exhibit lower overpotentials at 10 mA cm À 2 (η = 0.34 V) and medium current densities of 100 mA cm À 2 (η = 0.40 V) compared to the corresponding brucite-type hydroxides and LDH materials.

Electrooxidation of Alcohols on Mixed Copper–Cobalt Hydroxycarbonates in Alkaline Solution

“…In order to estimate the faradaic currents of OER from DEMS signals, the relationship between the m / z 32 DEMS signals and the corresponding O 2 faradaic currents was investigated by a proper calibration. The calibration was conducted with a reported active and stable OER catalyst, a Co‐hydroxynitrate [79] , in an alcohol‐free 1 M KOH solution. This catalyst provided 100 % of OER faradaic efficiency in 1 M KOH at least up to 50 mA cm −2 .…”

Identification of non-traditional coordination environments for iron ions in nickel hydroxide lattices

“…33 Parallel studies have identified non-traditional coordination sites in nominally LDH materials, including iron ions situated outside of the 2-dimensional framework in Co(OH) 2 , 34 iron ions on terrace sites of g-NiOOH, 35 and iridium ions anchored to the basal plane of Ni(OH) 2 . 36 Changes in behavior have also been achieved by mixing of nickel hydroxide and iron oxyhydroxide, 35 inclusion or exchange of anions between the LDH layers, [37][38][39] and through combination of anion exchange with immobilization of single Pt atoms. 40 The diversity of possibilities motivated us to explore variations in fabrication protocols as a means to study small changes in composition-dependent structure in an effort to identify nontraditional coordination environments in nickel-based layered double hydroxides.…”

Cobalt nickel boride as electrocatalyst for the oxidation of alcohols in alkaline media

“…DEMS signals shown are background subtracted. The calibration of the m/z 32 DEMS signals and the corresponding O 2 faradaic current densities (j Oxygen ) was conducted with a reported active and stable OER catalyst, a Co-hydroxynitrate [68], in an alcohol-free 1 M KOH solution. The following expression was found:…”